Aqueous solution of aminated silanol compound, use thereof, and process for producing the same

ABSTRACT

The present invention relates to aqueous solutions of amino group-containing silanol compounds, glass substrates and glass fibers which are surface-treated with the solutions, and processes for the preparation of aqueous solutions of amino-containing silanol compounds. 
     The aqueous solutions of amino group-containing silanol compounds of the present invention are prepared by reacting 1 mole of an aminoalkylsilane with 1.5 to 10 moles of water, and distilling off a volatile organic compound by-producing during the reaction until the content becomes less than 4% by weight.

TECHNICAL FIELD

This invention relates to aqueous solutions of amino group-containingsilanol compounds, glass substrates and glass fibers which aresurface-treated with the solutions, and processes for the preparation ofaqueous solutions of amino-containing silanol compounds.

BACKGROUND ART

Hydrolyzable silanes which have been extensively used as silane couplingagents and surface treating agents for various substrates are utilizedafter a hydrolyzable group in the silanes has been hydrolyzed.

Japanese Patent No. 2508554 discloses, as an example of suchhydrolyzable silanes, aqueous solutions of amino group-containingsilanol compounds prepared by hydrolyzing aminoalkoxysilanes andremoving by-producing alcohols. The amino group-containing silanolcompounds, which have undergone the hydrolysis and removal of theby-producing alcohols, are materials wherein a volatile organic compoundsuch as an alcohol is relatively difficult to generate when used in thesurface treatment.

However, the aqueous solutions of amino group-containing silanolcompounds disclosed in Japanese Patent No. 2508554 might lack storagestability, depending on storage conditions. Moreover, when the aqueoussolutions of amino group-containing silanol compounds were allowed tostand in contact with air, ethyl alcohol exceeding 1000 ppm (0.1 MPa,25° C.) which is an allowable concentration advised by the AmericanConference of Governmental Industrial Hygienists (ACGIH) might beemitted into air, depending on the conditions under which they areallowed to stand.

DISCLOSURE OF THE INVENTION

We have made intensive studies in view of the problems in theabove-mentioned prior art, and found that an aqueous solution of anamino group-containing silanol compound containing less than 4% byweight of a by-producing volatile organic compound is excellent instorage stability and can control the emission of a volatile organiccompound into air below the allowable concentration, said silanolcompound being prepared by reacting 1 mole of an aminoalkyl silanerepresented by the formula (1) with 1.5 to 10 moles of water anddistilling off a volatile organic compound by-producing during thereaction. The present invention has been accomplished on the basis ofthis finding.

H₂N(CH₂)_(n)Si(R)₃  (1)

wherein R is a hydrolyzable group and n is an integer of 1-6.

The present invention is composed of the following items (1) to (14).

(1) An aqueous solution of an amino group-containing silanol compoundcontaining less than 4% by weight of a by-producing volatile organiccompound, prepared by reacting 1 mole of an aminoalkylsilane representedby the formula (1) with 1.5 to 10 moles of water and distilling off avolatile organic compound by-producing during the reaction.

H₂N(CH₂)_(n)Si (R)₃  (1)

 wherein R is a hydrolyzable group and n is an integer of 1 to 6.

(2) The aqueous solution of an amino group-containing silanol compoundcontaining less than 4% by weight of a by-producing volatile organiccompound according to the item 1, wherein the content of silicon is inthe range of 7.5 to 17% by weight.

(3) The aqueous solution of an amino group-containing silanol compoundcontaining less than 4% by weight of a by-producing volatile organiccompound according to the item 1, wherein it is prepared using anaminoalkylsilane of the formula (1) wherein R is an alkylalkoxy group of1 to 4 carbon atoms.

(4) The aqueous solution of an amino group-containing silanol compoundcontaining less than 4% by weight of a by-producing volatile organiccompound according to the item 1, wherein it is prepared by carrying outthe reaction of an aminoalkylsilane with water and the removal of aby-producing volatile organic compound by distillation in the range of 0to 150° C.

(5) The aqueous solution of an amino group-containing silanol compoundcontaining less than 4% by weight of a by-producing volatile organiccompound according to the item 1, wherein it is prepared by distillingoff a by-producing volatile organic compound under reduced pressure inthe range of 1 Pa to 0.1 MPa.

(6) The aqueous solution of an amino group-containing silanol compoundcontaining less than 4% by weight of a by-producing volatile organiccompound according to the item 1, wherein it is prepared by adding to areaction solution water of the same weight as the volatile organiccompound distilled off from the reaction solution, in the distillationof the by-producing volatile organic compound.

(7) A surface treating agent comprising the aqueous solution of an aminogroup-containing silanol compound as defined in any one of the precedingitems 1 to 6.

(8) A glass substrate which is surface treated with the aqueous solutionof an amino group-containing silanol compound as defined in any one ofthe preceding items 1 to 6.

(9) A glass fiber which is surface treated with the aqueous solution ofan amino group-containing silanol compound as defined in any one of thepreceding items 1 to 6.

(10) A process for the preparation of an aqueous solution of an aminogroup-containing silanol compound, which comprises reacting 1 mole of anaminoalkylsilane of the formula (1) as set forth in the item 1 with 1.5to 10 moles of water and distilling off a volatile organic compoundby-producing during the reaction until its content is less than 4% byweight.

(11) The process for the preparation of an aqueous solution of an aminogroup-containing silanol compound according to the item 10, wherein theaminoalkylsilane of the formula (1) as defined in the item 1 wherein Ris an alkylalkoxy group of 1 to 4 carbon atoms is used.

(12) The process for the preparation of an aqueous solution of an aminogroup-containing silanol compound according to the item 10, wherein thereaction of an aminoalkylsilane with water and the removal of aby-producing volatile organic compound by distillation are carried outin the range of 0 to 150° C.

(13) The process for the preparation of an aqueous solution of an aminogroup-containing silanol compound according to the item 10, wherein theby-producing volatile organic compound is distilled off under reducedpressure in the range of 1 Pa to 0.1 MPa.

(14) The process for the preparation of an aqueous solution of an aminogroup-containing silanol compound according to the item 10, whereinwater of the same weight as the volatile organic compound removed bydistillation from a reaction solution is added to the reaction solution,in the distillation of the by-producing volatile organic compound.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ²⁹Si-NMR chart before dilution of an aqueous solution of anamino group-containing silanol compound.

FIG. 2 is a ²⁹Si-NMR chart after dilution of an aqueous solution of anamino group-containing silanol compound.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is described in detail below.

In the formula (I) of the invention, n is an integer of 1 to 6,preferably 1 to 4, and more preferably 3. A hydrolyzable silanecontaining an aminopropyl group wherein n is 3 has goodwater-solubility. The aminoalkyl silanes represented by the formula (1)according to the invention may be commercially available ones.

In the invention, R in the formula (1) is not particularly limited, solong as it is a hydrolyzable group. Preferably, R is an alkylalkoxygroup of not more than 4 carbon atoms. Examples of such a hydrolyzablegroup include methoxy, ethoxy, isopropoxy and the like. If R is analkylalkoxy group of not more than 4 carbon atoms, a volatile organiccompound producing by the hydrolysis has a relatively low boiling point,and is easily removed from the reaction solution.

In the reaction of the aminoalkoxysilane of the formula (1) with water(hydrolysis reaction), if the proportion of water used in the reactionis less than 1.5 moles per one mole of the aminoalkoxysilane, thereaction may not proceed sufficiently and the hydrolyzable group mayremain unreacted. If the proportion exceeds 10 moles per one mole of theaminoalkoxysilane, the efficiency in the distillation of the volatileorganic compound subsequent to the hydrolysis reaction may deteriorate.

In the invention, the temperature for the hydrolysis is not particularlylimited, but it is preferably in the range of 0 to 150° C., morepreferably 40 to 120° C.

A method for distilling off the volatile organic compound by-producingin the hydrolysis reaction is not particularly limited, but thedistillation is carried out preferably under the pressure of 1 Pa to 0.1MPa. The temperature is preferably in the range of 0 to 150° C., morepreferably 40 to 120° C., but not limited thereto.

In the invention, the by-producing volatile organic compound isdistilled off until its content becomes less than 4% by weight relativeto the aqueous solution of an amino group-containing silanol compound.The content of the organic compound is less than 4% by weight, but it ispreferably 2% by weight.

The temperature for the hydrolysis and the temperature for distillingoff the by-producing volatile organic compound are as described above.The hydrolysis and the distilling off are preferably carried out in therange of 0 to 150° C. in view of good efficiency and no deterioration ofthe product.

In the distillation of the by-producing volatile organic compoundaccording to the invention, it is preferable to add to a reactionsolution water of the same weight as the volatile organic compound to beremoved from the reaction solution by distillation. This addition canprevent condensation of the reaction solution and the resultant increasein the viscosity and reduction in the efficiency of distillation.

In the invention, the proportion of silicon contained in the aqueoussolution of an amino group-containing silanol compound is preferably inthe range of 7.5 to 17% by weight, based on the weight of the aqueoussolution. If it is more than 17% by weight, the viscosity of the aqueoussolution tends to exceedingly increase, thereby lowering theflowability, which leads to the difficulty in keeping the qualityconstant. If it is less than 7.5% by weight, the storage stability ofthe aqueous solution may decrease, resulting in the occurrence ofcoloration or the like.

The proportion of silicon contained in the aqueous solutions of an aminogroup-containing silanol compound can be controlled in such a mannerthat the concentration of an amino group-containing silanol compound isdetermined as a nonvolatile matter and adjusted to 30-67% by weight bydilution with water or by distillation operation. The proportion ofsilicon contained can be confirmed by a known method for measuring thecontent of silicon.

The aqueous solution of an amino group-containing silanol compoundaccording to the invention is clear and colorless or slightly yellowish.Since the content of the volatile organic compound upon the productionis less than 4% by weight, the emission of a volatile organic compoundinto air at ordinary temperature and pressure can be controlled belowthe allowable concentration advised by the American Conference ofGovernmental Industrial Hygienists (ACGIH). Since the by-producingvolatile organic compound is removed after complete hydrolysis of thehydrolyzable group, the content of the by-producing volatile organiccompound does not increase more than the level contained upon theproduction, even if said aqueous solution is diluted further with water.

After completion of the removal of the by-producing volatile organiccompound by distillation, the concentration of the aminogroup-containing silanol compounds in the reaction solution may bemeasured and, if necessary, adjusted to any level within the range notimpairing the effects of the invention by dilution with water or byconcentration with re-distillation.

As the concentration of the aqueous solution of an aminogroup-containing silanol compound is lower, the content of a silanetriolform having a monomer structure more increases. However, the aqueoussolution also contains an oligomer compound which is considered toimprove the film-forming properties of the solution when used as asurface treating agent. In addition, the aqueous solution of an aminogroup-containing silanol compound are very stable, and no alteration isobserved in the content of a volatile organic compound, the averagecomposition and appearance even after the storage test was carried out.

The aqueous solutions of an amino group-containing silanol compound areuseful as silane coupling agents or surface treating agents.

The composition and physical properties of the surface treating agentsof the invention are not particularly limited, so long as those agentscomprise the aqueous solution of an amino group-containing silanolcompound of the invention. The surface treating agents may containpigments, antifoaming agents, lubricants, preservatives, pH adjustors,film-forming agents, antistatic agents, antibacterial agents, surfaceactive agents, dyestuffs or the like, within the range not impairing theeffects of the invention.

The proportion of the aqueous solution of an amino group-containingsilanol compound contained in the surface treating agent of theinvention is preferably in the range of 0.1 to 50% by weight based onthe treating agent.

The uses of the aqueous solutions of an amino group-containing silanolcompound and the surface treating agents comprising the same caninclude, but not limited to, treatment of glass fibers, liquid sealingagents, casting molds, resin concrete, surface modification of resins,additives for water-based coatings or the like. When they are used inthe surface treatment of glass fibers and glass substrates such as glassplates, especially desirable effects are obtained due to good wettingand good adherence to the surface of glass substrates, which arecharacteristics of aminosilane.

EXAMPLES

The invention is further illustrated by the following examples.

Preparation of Aqueous Solution of an Amino Group-containing SilanolCompound

Example 1

In a 2-liter flask, equipped with a distillation column having a devicefor measuring a temperature at the top, a device for measuring aninternal temperature, a stirrer, a liquid feeding device, a cooler and areceiver for distillate, 1000 g of 3-aminopropyltriethoxysilane (SairaAce S330 manufactured by Chisso Corporation) were charged, and then 500g of deionized water were introduced from the liquid feeding device. Thepoint at which the peak of 3-aminopropyltriethoxysilane disappeared,indicating the completion of hydrolysis was determined by gaschromatography. Subsequently, the pressure within the reaction vesselwas reduced to 0.02 MPa, and a reaction solution in the flask was heatedto 60° C. to remove 500 g of ethanol by-produced. To remove traceamounts of residual ethanol, distillation was further continued toremove 250 g of ethanol distillate. Then, deionized water of the sameweight as the ethanol distillate was added to the reaction solution toadjust the concentration and viscosity, thereby affording an aqueoussolution of an amino group-containing silanol compound.

The reaction solution after completion of the distillation was analyzedby gas chromatography. The ethanol content was found to be not more than0.1% by weight. An aliquot of the aqueous solution of the aminogroup-containing silanol compound was measured into an aluminum cup andheated to dryness in a hot-air oven at 105° C. for 3 hrs. Thenonvolatile matter was found to be 50% by weight. It was found that thecontent of silicon in the aqueous solution of the amino group-containingsilanol compound was 12.7% by weight and the viscosity at 25° C. was 150mm²/s.

Example 2

In the same 2-liter flask as used in Example 1, 660 g of3-aminopropyltriethoxysilane (Saira Ace S330 manufactured by ChissoCorporation) were charged, and then 670 g of deionized water wereintroduced from the liquid feeding device. The point at which the peakof 3-aminopropyltriethoxysilane disappeared, indicating the completionof hydrolysis was determined by gas chromatography. Subsequently, thepressure within the reaction vessel was reduced to 0.02 MPa, and areaction solution in the flask was heated to 60° C. to remove 330 g ofethanol by-produced. To remove trace amounts of residual ethanol,distillation was further continued to remove 250 g of ethanoldistillate. Then, deionized water of the same weight as the ethanoldistillate was added to the reaction solution to adjust theconcentration and viscosity, thereby affording an aqueous solution of anamino group-containing silanol compound.

The aqueous solution of the amino group-containing silanol compoundafter completion of the distillation was analyzed by gas chromatography.The ethanol content was found to be not more than 0.1% by weight. Analiquot of the aqueous solution of the amino group-containing silanolcompound was measured into an aluminum cup and heated to dryness in ahot-air oven at 105° C. for 3 hrs. The nonvolatile matter was found tobe 33% by weight. It was found that the content of silicon in theaqueous solution of the amino group-containing silanol compound was 8.2%by weight and the viscosity at 25° C. was 9 mm²/s.

Comparative Example 1

In the same 2-liter flask as used in Example 1, 400 g of3-aminopropyltriethoxysilane (Saira Ace S330 manufactured by ChissoCorporation) were charged, and then 800 g of deionized water wereintroduced from the liquid feeding device. The point at which the peakof 3-aminopropyl triethoxysilane disappeared, indicating the completionof hydrolysis was determined by gas chromatography. Subsequently, thepressure within the reaction vessel was reduced to 0.02 MPa, and areaction solution in the flask was heated to 60° C. to remove 200 g ofethanol by-produced. To remove trace amounts of residual ethanol,distillation was further continued to remove 250 g of ethanoldistillate. Then, deionized water of the same weight as the ethanoldistillate was added to the reaction solution to adjust theconcentration and viscosity, thereby affording an aqueous solution of anamino group-containing silanol compound.

The reaction solution after completion of the distillation was analyzedby gas chromatography. The ethanol content was found to be not more than0.1% by weight. An aliquot of the aqueous solution of the aminogroup-containing silanol compound was measured into an aluminum cup andheated to dryness in a hot-air oven at 105° C. for 3 hrs. Thenonvolatile matter was found to be 20% by weight. It was found that thecontent of silicon in the aqueous solution of the amino group-containingsilanol compound was 5.1% by weight and the viscosity at 25° C. was 2mm²/s.

Storage Test

After the aqueous solutions of the amino group-containing silanolcompound prepared in Examples 1, 2 and Comparative Example 1 were storedat 40° C. for 180 days, the analysis of the viscosity, composition andalcohol content was carried out.

For the solutions of Examples 1, 2 and Comparative Example 1, theviscosity was constant for 180 days. (Table 1). The viscosity wasmeasured in accordance with JIS Z 8803.

During the storage period of 180 days, an increase in the alcoholcontent was not observed in the aqueous solutions of Examples 1, 2 andComparative Example 1 (Table 2). The alcohol content was measured by gaschromatography.

For the aqueous solutions of the amino group-containing silanol compoundprepared in Examples 1 and 2, no coloration was detectable by visualobservation. For the aqueous solution of the amino group-containingsilanol compound prepared in Comparative Example 1, however, theanalysis value for coloration (haze) varied 20 or more, and yellowingwas apparently observed by visual observation (Table 3). The colorationanalysis was determined in accordance with JIS K0071.

From the results of these storage tests, it was found that the aqueoussolutions of the amino group-containing silanol compound prepared by theinvention were very stable.

TABLE 1 Viscosity (10⁻⁶ m²/s 25° C.) Comparative Lapsed days (day)Example 1 Example 2 Example 1  0 150 9 2  90 151 9 3 180 149 9 2

TABLE 2 Alcohol content (% by weight) Comparative Lapsed days (day)Example 1 Example 2 Example 1  0 <0.1 <0.1 <0.1  90 <0.1 <0.1 <0.1 180<0.1 <0.1 <0.1

TABLE 3 After storage Before storage test of 180 days AppearanceAppearance (Visual Color (Visual Color Sample observation) (Haze)observation) (Haze) Example 1 Colorless, 30 Colorless, 30 clear clearExample 2 Colorless, 30 Colorless, 30 clear clear Comparative Colorless,30 Yellow, 50 Example 1 clear clear

Analysis of Alcohol Content

The aqueous solution of the amino group-containing silanol compoundprepared in Example 1 (50% by weight of nonvolatile matter) was dilutedwith deionized water such that the nonvolatile matter was 33%, 20%, 10%and 1% by weight. By analysis of the alcohol content by gaschromatography, no formation of alcohol was observed.

Analysis of Composition of Effective Compound

An average composition of each diluted solution prepared in the above“Analysis of alcohol content” was analyzed by ²⁹Si-NMR. When the aqueoussolution of the amino group-containing silanol compound prepared inExample 1 was diluted to make the concentration of the compound lower,the silane triol form increased as compared with the original aqueoussolution of the amino group-containing silanol compound (Example 1).Especially when the aqueous solution was diluted to 1% by weight of thenonvolatile matter, 45 mole % of the composition was composed of thesilane triol form (FIG. 1, FIG. 2). However, 55 mole % of an oligomercompound was present, which exhibited good film-forming properties whenthe aqueous solution was used as a surface treating agent.

Accordingly, it was found that the aqueous solutions of aminogroup-containing silanol compounds of the present invention did notproduce alcohol even diluted with water, and that they containedsufficiently the oligomer compound as the effective compound for thesurface treatment (Table 4).

TABLE 4 Concentration of nonvolatile matter Content of oligomer (% byweight) form (mol %) 50 99 33 98 20 96 10 90  1 55

Evaluation as a Surface Treating Agent

Surface treating agent (1) having 5% by weight of nonvolatile matter wasprepared by adding 90 g of deionized water to 5 g of the aqueoussolution of the amino group-containing silanol compound prepared inExample 1. For comparison, Surface treating agent (2) having 5% byweight of nonvolatile matter was prepared by adding 95 g of deionizedwater to 5 g of 3-aminopropyltriethoxysilane (Saira Ace S330manufactured by Chisso Corporation).

Each of the surface treating agents was stirred for one hour, and thencoated onto a slide glass and the wetting property was evaluated byvisual observation. The slide glass was washed successively with adetergent, deionized water, acetone and deionized water, and air-dried.The coating of the surface treating agent was carried out by dipping. Asa result, it was found that there was no difference in the wettingproperty in each concentration, and the performance was hold even if thevolatile organic compound (VOC) was reduced (Table 5).

TABLE 5 Sample Evaluation Surface treating agent (1): prepared fromExample 1 ∘ Surface treating agent (2): prepared from 3-amino- ∘propyltriethoxysilane

INDUSTRIAL APPLICABILITY

The aqueous solutions of amino group-containing silanol compounds of thepresent invention are excellent in storage stability and can control theemission of a volatile organic compound into air below the allowableconcentration. Further, the surface treating agents of the presentinvention contain very low volatile organic compounds, and hence aresuitable as easily disposable surface treating agents when used in thetreatment of glass fibers in which aminosilanes have been used, liquidsealing agents, casting molds, resin concrete, surface modification ofresins, additives for water-based coatings or the like.

What is claimed is:
 1. An aqueous solution of an amino group-containingsilanol compound containing less than 4% by weight of a by-producingvolatile organic compound, prepared by reacting 1 mole of anaminoalkylsilane represented by the formula (1) with 1.5 to 10 moles ofwater and distilling off a volatile organic compound by-producing duringthe reaction: H₂N(CH₂)_(n)Si(R)₃  (1) wherein R is a hydrolyzable groupand n is an integer of 1 to
 6. 2. The aqueous solution of an aminogroup-containing silanol compound containing less than 4% by weight of aby-producing volatile organic compound according to claim 1, wherein thecontent of silicon is in the range of 7.5 to 17% by weight.
 3. Theaqueous solution of an amino group-containing silanol compoundcontaining less than 4% by weight of a by-producing volatile organiccompound according to claim 1, wherein it is prepared with anaminoalkylsilane of the formula (1) wherein R is an alkylalkoxy group of1 to 4 carbon atoms.
 4. The aqueous solution of an aminogroup-containing silanol compound containing less than 4% by weight of aby-producing volatile organic compound according to claim 1, wherein itis prepared by carrying out the reaction of an aminoalkylsilane withwater and the removal of a by-producing volatile organic compound bydistillation, in the range of 0 to 150° C.
 5. The aqueous solution of anamino group-containing silanol compound containing less than 4% byweight of a by-producing volatile organic compound according to claim 1,wherein it is prepared by distilling off a by-producing volatile organiccompound under reduced pressure in the range of 1 Pa to 0.1 MPa.
 6. Theaqueous solution of amino group-containing silanol compounds containingless than 4% by weight of a by-producing volatile organic compoundaccording to claim 1, wherein it is prepared by adding to a reactionsolution water of the same weight as the volatile organic compound to beremoved by distillation from the reaction solution, in the distillationof the by-producing volatile organic compound.
 7. A surface treatingagent comprising the aqueous of an amino group-containing silanolcompound as defined in claim
 1. 8. A glass substrate which is surfacetreated with the aqueous solution of an amino group-containing silanolcompound as defined in claim
 1. 9. A glass fiber which is surfacetreated with the aqueous solution of an amino group-containing silanolcompound as defined in claim
 1. 10. A process for the preparation of anaqueous solution of an amino group-containing silanol compound, whichcomprises reacting 1 mole of an aminoalkylsilane represented by theformula (1) as set forth in claim 1 with 1.5 to 10 moles of water anddistilling off a volatile organic compound by-producing during thereaction until its content becomes less than 4% by weight.
 11. Theprocess for the preparation of an aqueous solution of an aminogroup-containing silanol compound according to claim 10, wherein theaminoalkylsilane of the formula (1) as defined in claim 1 wherein R isan alkylalkoxy group of 1 to 4 carbon atoms is used.
 12. The process forthe preparation of an aqueous solution of an amino group-containingsilanol compound according to claim 10, wherein the reaction of anaminoalkylsilane with water and the removal of a by-producing volatileorganic compound by distillation are carried out in the range of 0 to150° C.
 13. The process for the preparation of an aqueous solution of anamino group-containing silanol compound according to claim 10, whereinthe by-producing volatile organic compound is distilled off underreduced pressure in the range of 1 Pa to 0.1 MPa.
 14. The process forthe preparation of an aqueous solution of an amino group-containingsilanol compound according to claim 10, wherein water of the same weightas the volatile organic compound removed by distillation from a reactionsolution is added to the reaction solution, in the distillation of theby-producing volatile organic compound.